The Experimental Irradiator Core maintains and operates sources of ionizing and non-ionizing radiation for use of Cancer Center members in their experimental studies. Studies performed by the resource staff include advice to users on design of experiments using radiation, training in operation of the sources, scheduling use of the resources, operating the resources when necessary, dosimetry for new experimental setups, and maintenance and repair of the resources. When not in use by members, these facilities and services are also available to non-members on an increased fee-basis. The primary resources of the facility are four Cs-137 irradiators that deliver ionizing radiation. Two Nordion Gammacell 40 irradiators are primarily used for whole-body irradiation of rodents and cell cultures at a constant dose rate. The Shepherd Mark I irradiator is primarily used to deliver radiation to animal tumors at doses compared to those used clinically in external beam radiotherapy or to sterilized cell cultures or other experimental samples. The low-dose-rate-irradiator, built-in-house, is used to deliver radiation to cell cultures and rodents in dose-rates similar to those used in tumor therapy using radioactive implants, and has been used in studies of carcinogenic processes by low- dose-rate radiation.